Catalyst and method for fractionating lignocellulosic material

ABSTRACT

Various embodiments disclosed relate to solid catalysts that convert lignocellulosic material to monomer sugars that are suitable for fermentation. The solid catalysts include a transition metal complex attached to a magnetic bead, and can be physically separated from a fermentation mixture and reused several times.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 62/536,065 entitled “LIGNIN UPGRADE FOR HIGHCHEMICAL AND SUGAR PRODUCTION,” filed Jul. 24, 2017, the disclosure ofwhich is incorporated herein in its entirety by reference.

BACKGROUND

Over 2×10¹¹ metric tons of lignocellulosic material is produced bynatural source annually. As feedstock, this material would providetheoretical energy of 3×10¹⁸ kJ, which corresponds to ten times annualenergy consumption of the entire world. In order to tap such energyresources, key technology must be developed, namely, that of improvedproduction of green sugars for subsequent generation of green fuel andchemicals by biological conversion. Cellulosic ethanol became a realityin 2015, when several corn ethanol plants developed new “bolt-on”processes with multiple, onsite production lines for producing fuel andchemicals. (RFA, Fueling a high octane future. 2016, Renewable FuelsAssociation) Commercial cellulose-based sugar production was a turningpoint from process scale up and demonstration. However, lignocellulosicpretreatment, either by thermal or chemical means, is necessary toconvert biomass so that it is accessible for enzymatic action.Unfortunately, current processes are complex and require high capitalexpenditure (CAPEX) and operational expenditures (OPEX). The need for asimple, economical conversion method is urgent.

Existing processes typically use homogenous acids, such as H₂SO₄ or HCl,and biological enzymes to convert lignocellulose into green sugars.However, these tools are burdened by many technical and economicproblems.

There is a need to develop processes that will dramatically reduce theprocessing cost and time for converting lignocellulosic into fermentablesugars, thus providing an effective feedstock for biofuels and bio-basedchemicals. Solid acid catalysts provide certain advantages and maypermit cost of biofuel to reduce below that of petroleum-derivedgasoline once implemented by biofuel producers based on lignocellulosicfeedstock.

Several solid catalysts are known, such as acid resins, metal oxides,and zeolites, that fractionate cellulose into sugars and variousoligomers. (Li et al., 2016; Hu et al., 2016; Rinaldo et al., 2010;Schneider et al., 2016) However, despite their potential, there is adilemma with using solid acid catalysts. Specifically, solid acidcatalysts have a problem of low substrate load (Schneider et al., 2016;Verma et al., 2014; Shuai et al., 2012), poor reaction mediums or lowyields of specific mono sugars. (Hu et al., 2016; Rinaldi et al., 2010;Onda et al., 2008; Zhang et al., 2014) To date, typical celluloseloading has been limited to less than 15%. Additionally, some solidcatalysts have a problem of low or no yield of mono sugars, for example,core-shell Fe₃O₄@SiO₂—SO₃H acid catalyst reports high turnover ofreducing sugars but no report of mono sugar hydrolysis.

Thus, there is a need for an improved method which more efficientlyfractionates lignocellulosic material into green sugars and high valuechemicals. The present disclosure describes a solution which solid phasecatalyst that incorporates a transition metal complex and magneticproperties that can dramatically reduce the processing cost and time tocreate fermentable sugars from lignocellulosic biomass to producebiofuels and bio-based chemicals. The inventive catalysts can functionunder high cellulose load and have low catalyst loading requirements,while also producing monosaccharides.

Thus, there is a need for an improved method which more efficientlyfractionates lignocellulosic material into green sugars and high valuechemicals. The present disclosure describes a solution that dramaticallyreduces the processing cost and time to create fermentable sugars fromlignocellulosic biomass, thus providing a green and economical feedstockfor biofuel and bio-based chemical production.

SUMMARY OF THE INVENTION

The present invention provides a catalyst linked to a magnetic beadcomprising iron oxide, the catalyst having the structure of Formula I.

In Formula I, X is a counterion, L is a linker group, MB is ametal-containing bead, and R¹ and R² are each independently chosen fromC₁₋₁₀ alkyl, C₇₋₁₀ aralkyl, C₆-C₁₂ aryl, C₂₋₈ heterocyclyl, andcombinations thereof, each of which may be optionally substituted,wherein at least a portion of the surface of the bead is uniformlycoated with amorphous silica.

In some embodiments, a method of fractionation is provided. The methodincludes treating a lignin-containing and/or cellulose-containingcomposition with an effective amount of a catalyst that includesmetal-containing bead linked to a transition metal complex to form afractionated composition.

In some embodiments, the method of fractionation includes mechanicallyand chemically fractionating a cellulose-containing composition with acatalytic amount of the a catalyst that includes metal-containing beadlinked to a transition metal complex to produce a fractionatedcomposition having a liquid phase comprising monosaccharides and a solidphase, wherein the chemical fractionation includes selective cleavage ofthe β-1,4 glycosidic bonds of cellulose by the transition metal complex,the mechanical fractionation includes increasing the accessible surfacearea and pore size of the cellulose-containing composition; andmagnetically separating a catalyst that includes metal-containing beadlinked to a transition metal complex from the fractionated composition.

In some embodiments a method of making a transition metal complex isprovided. The method includes reacting

with a transition metal precursor in the presence a strong base andsolvent to form a N-heterocyclic carbene complex.

Advantageously, in some embodiments, the same catalyst can be re-usedmultiple times and can be conveniently recovered and isolated from areaction mixture using a magnet. Advantageously, the catalyst functionsunder high cellulose loads of as much as 50%.

The present disclosure describes, in various embodiments, a method whichhas the advantage of dramatically reducing the processing cost and timeto create fermentable sugars from lignocellulosic biomass. For example,in various embodiments, the fractionation can be performed directly onwood and other lignocellulosic materials without requiring a separatestep to separate lignin. The present disclosure also describes, invarious embodiments, catalysts which can function under high celluloseload and have low catalyst loading requirements, while also producingmonosaccharides.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to certain embodiments of thedisclosed subject matter. While the disclosed subject matter will bedescribed in conjunction with the enumerated claims, it will beunderstood that the exemplified subject matter is not intended to limitthe claims to the disclosed subject matter.

Throughout this document, values expressed in a range format should beinterpreted in a flexible manner to include not only the numericalvalues explicitly recited as the limits of the range, but also toinclude all the individual numerical values or sub-ranges encompassedwithin that range as if each numerical value and sub-range is explicitlyrecited. For example, a range of “about 0.1% to about 5%” or “about 0.1%to 5%” should be interpreted to include not just about 0.1% to about 5%,but also the individual values (e.g., 1%, 2%, 3%, and 4%) and thesub-ranges (e.g., 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within theindicated range. The statement “about X to Y” has the same meaning as“about X to about Y,” unless indicated otherwise. Likewise, thestatement “about X, Y, or about Z” has the same meaning as “about X,about Y, or about Z,” unless indicated otherwise.

In this document, the terms “a,” “an,” or “the” are used to include oneor more than one unless the context clearly dictates otherwise. The term“or” is used to refer to a nonexclusive “or” unless otherwise indicated.The statement “at least one of A and B” or “at least one of A or B” hasthe same meaning as “A, B, or A and B.” In addition, it is to beunderstood that the phraseology or terminology employed herein, and nototherwise defined, is for the purpose of description only and not oflimitation. Any use of section headings is intended to aid reading ofthe document and is not to be interpreted as limiting; information thatis relevant to a section heading may occur within or outside of thatparticular section.

In the methods described herein, the acts can be carried out in anyorder without departing from the principles of the invention, exceptwhen a temporal or operational sequence is explicitly recited.Furthermore, specified acts can be carried out concurrently unlessexplicit claim language recites that they be carried out separately. Forexample, a claimed act of doing X and a claimed act of doing Y can beconducted simultaneously within a single operation, and the resultingprocess will fall within the literal scope of the claimed process.

The term “about” as used herein can allow for a degree of variability ina value or range, for example, within 10%, within 5%, or within 1% of astated value or of a stated limit of a range, and includes the exactstated value or range.

The term “substantially” as used herein refers to a majority of, ormostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%,98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more, or100%. The term “substantially free of” as used herein can mean havingnone or having a trivial amount of, such that the amount of materialpresent does not affect the material properties of the compositionincluding the material, such that the composition is about 0 wt % toabout 5 wt % of the material, or about 0 wt % to about 1 wt %, or about5 wt % or less, or less than, equal to, or greater than about 4.5 wt %,4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1,0.01, or about 0.001 wt % or less. The term “substantially free of” canmean having a trivial amount of, such that a composition is about 0 wt %to about 5 wt % of the material, or about 0 wt % to about 1 wt %, orabout 5 wt % or less, or less than, equal to, or greater than about 4.5wt %, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2,0.1, 0.01, or about 0.001 wt % or less, or about 0 wt %.

The term “organic group” as used herein refers to any carbon-containingfunctional group. Examples can include an oxygen-containing group suchas an alkoxy group, aryloxy group, aralkyloxy group, oxo(carbonyl)group; a carboxyl group including a carboxylic acid, carboxylate, and acarboxylate ester; a sulfur-containing group such as an alkyl and arylsulfide group; and other heteroatom-containing groups. Non-limitingexamples of organic groups include OR, OOR, OC(O)N(R)₂, CN, CF₃, OCF₃,R, C(O), methylenedioxy, ethylenedioxy, N(R)₂, SR, SOR, SO₂R, SO₂N(R)₂,SO₃R, C(O)R, C(O)C(O)R, C(O)CH₂C(O)R, C(S)R, C(O)OR, OC(O)R, C(O)N(R)₂,OC(O)N(R)₂, C(S)N(R)₂, (CH₂)₀₋₂N(R)C(O)R, (CH₂)₀₋₂N(R)N(R)₂,N(R)N(R)C(O)R, N(R)N(R)C(O)OR, N(R)N(R)CON(R)₂, N(R)SO₂R, N(R)SO₂N(R)₂,N(R)C(O)OR, N(R)C(O)R, N(R)C(S)R, N(R)C(O)N(R)₂, N(R)C(S)N(R)₂,N(COR)COR, N(OR)R, C(═NH)N(R)₂, C(O)N(OR)R, C(═NOR)R, and substituted orunsubstituted (C₁-C₁₀₀)hydrocarbyl, wherein R can be hydrogen (inexamples that include other carbon atoms) or a carbon-based moiety, andwherein the carbon-based moiety can be substituted or unsubstituted.

The term “substituted” as used herein in conjunction with a molecule oran organic group as defined herein refers to the state in which one ormore hydrogen atoms contained therein are replaced by one or morenon-hydrogen atoms. The term “functional group” or “substituent” as usedherein refers to a group that can be or is substituted onto a moleculeor onto an organic group. Examples of substituents or functional groupsinclude, but are not limited to, a halogen (e.g., F, Cl, Br, and I); anoxygen atom in groups such as hydroxy groups, alkoxy groups, aryloxygroups, aralkyloxy groups, oxo(carbonyl) groups, carboxyl groupsincluding carboxylic acids, carboxylates, and carboxylate esters; asulfur atom in groups such as thiol groups, alkyl and aryl sulfidegroups, sulfoxide groups, sulfone groups, sulfonyl groups, andsulfonamide groups; a nitrogen atom in groups such as amines,hydroxyamines, nitriles, nitro groups, N-oxides, hydrazides, azides, andenamines; and other heteroatoms in various other groups. Non-limitingexamples of substituents that can be bonded to a substituted carbon (orother) atom include F, Cl, Br, I, OR, OC(O)N(R)₂, CN, NO, NO₂, ONO₂,azido, CF₃, OCF₃, R, O (oxo), S (thiono), C(O), S(O), methylenedioxy,ethylenedioxy, N(R)₂, SR, SOR, SO₂R, SO₂N(R)₂, SO₃R, C(O)R, C(O)C(O)R,C(O)CH₂C(O)R, C(S)R, C(O)OR, OC(O)R, C(O)N(R)₂, OC(O)N(R)₂, C(S)N(R)₂,(CH₂)₀₋₂N(R)C(O)R, (CH₂)₀₋₂N(R)N(R)₂, N(R)N(R)C(O)R, N(R)N(R)C(O)OR,N(R)N(R)CON(R)₂, N(R)SO₂R, N(R)SO₂N(R)₂, N(R)C(O)OR, N(R)C(O)R,N(R)C(S)R, N(R)C(O)N(R)₂, N(R)C(S)N(R)₂, N(COR)COR, N(OR)R, C(═NH)N(R)₂,C(O)N(OR)R, and C(═NOR)R, wherein R can be hydrogen or a carbon-basedmoiety; for example, R can be hydrogen, (C₁-C₁₀₀)hydrocarbyl, alkyl,acyl, cycloalkyl, aryl, aralkyl, heterocyclyl, heteroaryl, orheteroarylalkyl; or wherein two R groups bonded to a nitrogen atom or toadjacent nitrogen atoms can together with the nitrogen atom or atomsform a heterocyclyl.

The term “alkyl” as used herein refers to straight chain and branchedalkyl groups and cycloalkyl groups having from 1 to 40 carbon atoms, 1to about 20 carbon atoms, 1 to 12 carbons or, in some embodiments, from1 to 8 carbon atoms. Examples of straight chain alkyl groups includethose with from 1 to 8 carbon atoms such as methyl, ethyl, n-propyl,n-butyl, n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples ofbranched alkyl groups include, but are not limited to, isopropyl,iso-butyl, sec-butyl, t-butyl, neopentyl, isopentyl, and2,2-dimethylpropyl groups. As used herein, the term “alkyl” encompassesn-alkyl, isoalkyl, and anteisoalkyl groups as well as other branchedchain forms of alkyl. Representative substituted alkyl groups can besubstituted one or more times with any of the groups listed herein, forexample, amino, hydroxy, cyano, carboxy, nitro, thio, alkoxy, andhalogen groups.

The term “alkenyl” as used herein refers to straight and branched chainand cyclic alkyl groups as defined herein, except that at least onedouble bond exists between two carbon atoms. Thus, alkenyl groups havefrom 2 to 40 carbon atoms, or 2 to about 20 carbon atoms, or 2 to 12carbon atoms or, in some embodiments, from 2 to 8 carbon atoms. Examplesinclude, but are not limited to vinyl, —CH═CH(CH₃), —CH═C(CH₃)₂,—C(CH₃)═CH₂, —C(CH₃)═CH(CH₃), —C(CH₂CH₃)═CH₂, cyclohexenyl,cyclopentenyl, cyclohexadienyl, butadienyl, pentadienyl, and hexadienylamong others.

The term “alkynyl” as used herein refers to straight and branched chainalkyl groups, except that at least one triple bond exists between twocarbon atoms. Thus, alkynyl groups have from 2 to 40 carbon atoms, 2 toabout 20 carbon atoms, or from 2 to 12 carbons or, in some embodiments,from 2 to 8 carbon atoms. Examples include, but are not limited to—C≡CH, —C≡C(CH₃), —C≡C(CH₂CH₃), —CH₂C≡CH, —CH₂C≡C(CH₃), and—CH₂C≡C(CH₂CH₃) among others.

The term “acyl” as used herein refers to a group containing a carbonylmoiety wherein the group is bonded via the carbonyl carbon atom. Thecarbonyl carbon atom is bonded to a hydrogen forming a “formyl” group oris bonded to another carbon atom, which can be part of an alkyl, aryl,aralkyl cycloalkyl, cycloalkylalkyl, heterocyclyl, heterocyclylalkyl,heteroaryl, heteroarylalkyl group or the like. An acyl group can include0 to about 12, 0 to about 20, or 0 to about 40 additional carbon atomsbonded to the carbonyl group. An acyl group can include double or triplebonds within the meaning herein. An acryloyl group is an example of anacyl group. An acyl group can also include heteroatoms within themeaning herein. A nicotinoyl group (pyridyl-3-carbonyl) is an example ofan acyl group within the meaning herein. Other examples include acetyl,benzoyl, phenylacetyl, pyridylacetyl, cinnamoyl, and acryloyl groups andthe like. When the group containing the carbon atom that is bonded tothe carbonyl carbon atom contains a halogen, the group is termed a“haloacyl” group. An example is a trifluoroacetyl group.

The term “cycloalkyl” as used herein refers to cyclic alkyl groups suchas, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, and cyclooctyl groups. In some embodiments, thecycloalkyl group can have 3 to about 8-12 ring members, whereas in otherembodiments the number of ring carbon atoms range from 3 to 4, 5, 6, or7. Cycloalkyl groups further include polycyclic cycloalkyl groups suchas, but not limited to, norbornyl, adamantyl, bornyl, camphenyl,isocamphenyl, and carenyl groups, and fused rings such as, but notlimited to, decalinyl, and the like. Cycloalkyl groups also includerings that are substituted with straight or branched chain alkyl groupsas defined herein. Representative substituted cycloalkyl groups can bemono-substituted or substituted more than once, such as, but not limitedto, 2,2-, 2,3-, 2,4-2,5- or 2,6-disubstituted cyclohexyl groups ormono-, di- or tri-substituted norbornyl or cycloheptyl groups, which canbe substituted with, for example, amino, hydroxy, cyano, carboxy, nitro,thio, alkoxy, and halogen groups. The term “cycloalkenyl” alone or incombination denotes a cyclic alkenyl group.

The term “aryl” as used herein refers to cyclic aromatic hydrocarbongroups that do not contain heteroatoms in the ring. Thus aryl groupsinclude, but are not limited to, phenyl, azulenyl, heptalenyl, biphenyl,indacenyl, fluorenyl, phenanthrenyl, triphenylenyl, pyrenyl,naphthacenyl, chrysenyl, biphenylenyl, anthracenyl, and naphthyl groups.In some embodiments, aryl groups contain about 6 to about 14 carbons inthe ring portions of the groups. Aryl groups can be unsubstituted orsubstituted, as defined herein. Representative substituted aryl groupscan be mono-substituted or substituted more than once, such as, but notlimited to, a phenyl group substituted at any one or more of 2-, 3-, 4-,5-, or 6-positions of the phenyl ring, or a naphthyl group substitutedat any one or more of 2- to 8-positions thereof.

The term “aralkyl” as used herein refers to alkyl groups as definedherein in which a hydrogen or carbon bond of an alkyl group is replacedwith a bond to an aryl group as defined herein. Representative aralkylgroups include benzyl and phenylethyl groups and fused(cycloalkylaryl)alkyl groups such as 4-ethyl-indanyl. Aralkenyl groupsare alkenyl groups as defined herein in which a hydrogen or carbon bondof an alkyl group is replaced with a bond to an aryl group as definedherein. The aralkyl group may be attached to the parent structure at anyposition of the aralkyl group. For example, a C₇-aralkyl may attach tothe parent structure so as to result in a linked benzyl group (i.e.,attached at a non-aromatic carbon) or attached so as to result in alinked toluenyl group (i.e. attached at a aromatic carbon). An exampleof a C₇-aralkyl is benzyl. An example of a C₈-aralkyl is phenylethyl.Aralkyl groups may be optionally substituted.

The term “heterocyclyl” as used herein refers to aromatic andnon-aromatic ring compounds containing three or more ring members, ofwhich one or more is a heteroatom such as, but not limited to, N, O, andS. Thus, a heterocyclyl can be a cycloheteroalkyl, or a heteroaryl, orif polycyclic, any combination thereof. In some embodiments,heterocyclyl groups include 3 to about 20 ring members, whereas othersuch groups have 3 to about 15 ring members. A heterocyclyl groupdesignated as a C₂-heterocyclyl can be a 5-ring with two carbon atomsand three heteroatoms, a 6-ring with two carbon atoms and fourheteroatoms and so forth. Likewise a C₄-heterocyclyl can be a 5-ringwith one heteroatom, a 6-ring with two heteroatoms, and so forth. Thenumber of carbon atoms plus the number of heteroatoms equals the totalnumber of ring atoms. A heterocyclyl ring can also include one or moredouble bonds. A heteroaryl ring is an embodiment of a heterocyclylgroup. The phrase “heterocyclyl group” includes fused ring speciesincluding those that include fused aromatic and non-aromatic groups. Forexample, a dioxolanyl ring and a benzdioxolanyl ring system(methylenedioxyphenyl ring system) are both heterocyclyl groups withinthe meaning herein. The phrase also includes polycyclic ring systemscontaining a heteroatom such as, but not limited to, quinuclidyl.Heterocyclyl groups can be unsubstituted, or can be substituted asdiscussed herein. Heterocyclyl groups include, but are not limited to,pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, pyrrolyl,pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, thiazolyl,pyridinyl, thiophenyl, benzothiophenyl, benzofuranyl,dihydrobenzofuranyl, indolyl, dihydroindolyl, azaindolyl, indazolyl,benzimidazolyl, azabenzimidazolyl, benzoxazolyl, benzothiazolyl,benzothiadiazolyl, imidazopyridinyl, isoxazolopyridinyl,thianaphthalenyl, purinyl, xanthinyl, adeninyl, guaninyl, quinolinyl,isoquinolinyl, tetrahydroquinolinyl, quinoxalinyl, and quinazolinylgroups. Representative substituted heterocyclyl groups can bemono-substituted or substituted more than once, such as, but not limitedto, piperidinyl or quinolinyl groups, which are 2-, 3-, 4-, 5-, or6-substituted, or disubstituted with groups such as those listed herein.

The term “heteroaryl” as used herein refers to aromatic ring compoundscontaining 5 or more ring members, of which, one or more is a heteroatomsuch as, but not limited to, N, O, and S; for instance, heteroaryl ringscan have 5 to about 8-12 ring members. A heteroaryl group is a varietyof a heterocyclyl group that possesses an aromatic electronic structure.A heteroaryl group designated as a C₂-heteroaryl can be a 5-ring withtwo carbon atoms and three heteroatoms, a 6-ring with two carbon atomsand four heteroatoms and so forth. Likewise a C₄-heteroaryl can be a5-ring with one heteroatom, a 6-ring with two heteroatoms, and so forth.The number of carbon atoms plus the number of heteroatoms sums up toequal the total number of ring atoms. Heteroaryl groups include, but arenot limited to, groups such as pyrrolyl, pyrazolyl, triazolyl,tetrazolyl, oxazolyl, isoxazolyl, thiazolyl, pyridinyl, thiophenyl,benzothiophenyl, benzofuranyl, indolyl, azaindolyl, indazolyl,benzimidazolyl, azabenzimidazolyl, benzoxazolyl, benzothiazolyl,benzothiadiazolyl, imidazopyridinyl, isoxazolopyridinyl,thianaphthalenyl, purinyl, xanthinyl, adeninyl, guaninyl, quinolinyl,isoquinolinyl, tetrahydroquinolinyl, quinoxalinyl, and quinazolinylgroups. Heteroaryl groups can be unsubstituted, or can be substitutedwith groups as is discussed herein. Representative substitutedheteroaryl groups can be substituted one or more times with groups suchas those listed herein.

Additional examples of aryl and heteroaryl groups include but are notlimited to phenyl, biphenyl, indenyl, naphthyl (1-naphthyl, 2-naphthyl),N-hydroxytetrazolyl, N-hydroxytriazolyl, N-hydroxyimidazolyl,anthracenyl (1-anthracenyl, 2-anthracenyl, 3-anthracenyl), thiophenyl(2-thienyl, 3-thienyl), furyl (2-furyl, 3-furyl), indolyl, oxadiazolyl,isoxazolyl, quinazolinyl, fluorenyl, xanthenyl, isoindanyl, benzhydryl,acridinyl, thiazolyl, pyrrolyl (2-pyrrolyl), pyrazolyl (3-pyrazolyl),imidazolyl (1-imidazolyl, 2-imidazolyl, 4-imidazolyl, 5-imidazolyl),triazolyl (1,2,3-triazol-1-yl, 1,2,3-triazol-2-yl 1,2,3-triazol-4-yl,1,2,4-triazol-3-yl), oxazolyl (2-oxazolyl, 4-oxazolyl, 5-oxazolyl),thiazolyl (2-thiazolyl, 4-thiazolyl, 5-thiazolyl), pyridyl (2-pyridyl,3-pyridyl, 4-pyridyl), pyrimidinyl (2-pyrimidinyl, 4-pyrimidinyl,5-pyrimidinyl, 6-pyrimidinyl), pyrazinyl, pyridazinyl (3-pyridazinyl,4-pyridazinyl, 5-pyridazinyl), quinolyl (2-quinolyl, 3-quinolyl,4-quinolyl, 5-quinolyl, 6-quinolyl, 7-quinolyl, 8-quinolyl), isoquinolyl(1-isoquinolyl, 3-isoquinolyl, 4-isoquinolyl, 5-isoquinolyl,6-isoquinolyl, 7-isoquinolyl, 8-isoquinolyl), benzo[b]furanyl(2-benzo[b]furanyl, 3-benzo[b]furanyl, 4-benzo[b]furanyl,5-benzo[b]furanyl, 6-benzo[b]furanyl, 7-benzo[b]furanyl),2,3-dihydro-benzo[b]furanyl (2-(2,3-dihydro-benzo[b]furanyl),3-(2,3-dihydro-benzo[b]furanyl), 4-(2,3-dihydro-benzo[b]furanyl),5-(2,3-dihydro-benzo[b]furanyl), 6-(2,3-dihydro-benzo[b]furanyl),7-(2,3-dihydro-benzo[b]furanyl), benzo[b]thiophenyl(2-benzo[b]thiophenyl, 3-benzo[b]thiophenyl, 4-benzo[b]thiophenyl,5-benzo[b]thiophenyl, 6-benzo[b]thiophenyl, 7-benzo[b]thiophenyl),2,3-dihydro-benzo[b]thiophenyl, (2-(2,3-dihydro-benzo[b]thiophenyl),3-(2,3-dihydro-benzo[b]thiophenyl), 4-(2,3-dihydro-benzo[b]thiophenyl),5-(2,3-dihydro-benzo[b]thiophenyl), 6-(2,3-dihydro-benzo[b]thiophenyl),7-(2,3-dihydro-benzo[b]thiophenyl), indolyl (1-indolyl, 2-indolyl,3-indolyl, 4-indolyl, 5-indolyl, 6-indolyl, 7-indolyl), indazole(1-indazolyl, 3-indazolyl, 4-indazolyl, 5-indazolyl, 6-indazolyl,7-indazolyl), benzimidazolyl (1-benzimidazolyl, 2-benzimidazolyl,4-benzimidazolyl, 5-benzimidazolyl, 6-benzimidazolyl, 7-benzimidazolyl,8-benzimidazolyl), benzoxazolyl (1-benzoxazolyl, 2-benzoxazolyl),benzothiazolyl (1-benzothiazolyl, 2-benzothiazolyl, 4-benzothiazolyl,5-benzothiazolyl, 6-benzothiazolyl, 7-benzothiazolyl), carbazolyl(1-carbazolyl, 2-carbazolyl, 3-carbazolyl, 4-carbazolyl),5H-dibenz[b,f]azepine (5H-dibenz[b,f]azepin-1-yl,5H-dibenz[b,f]azepine-2-yl, 5H-dibenz[b,f]azepine-3-yl,5H-dibenz[b,f]azepine-4-yl, 5H-dibenz[b,f]azepine-5-yl),10,11-dihydro-5H-dibenz[b,f]azepine(10,11-dihydro-5H-dibenz[b,f]azepine-1-yl,10,11-dihydro-5H-dibenz[b,f]azepine-2-yl,10,11-dihydro-5H-dibenz[b,f]azepine-3-yl,10,11-dihydro-5H-dibenz[b,f]azepine-4-yl,10,11-dihydro-5H-dibenz[b,f]azepine-5-yl), and the like.

The term “heterocyclylalkyl” as used herein refers to alkyl groups asdefined herein in which a hydrogen or carbon bond of an alkyl group asdefined herein is replaced with a bond to a heterocyclyl group asdefined herein. Representative heterocyclyl alkyl groups include, butare not limited to, furan-2-yl methyl, furan-3-yl methyl, pyridine-3-ylmethyl, tetrahydrofuran-2-yl ethyl, and indol-2-yl propyl.

The term “heteroarylalkyl” as used herein refers to alkyl groups asdefined herein in which a hydrogen or carbon bond of an alkyl group isreplaced with a bond to a heteroaryl group as defined herein.

The term “alkoxy” as used herein refers to an oxygen atom connected toan alkyl group, including a cycloalkyl group, as are defined herein.Examples of linear alkoxy groups include but are not limited to methoxy,ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, and the like. Examples ofbranched alkoxy include but are not limited to isopropoxy, sec-butoxy,tert-butoxy, isopentyloxy, isohexyloxy, and the like. Examples of cyclicalkoxy include but are not limited to cyclopropyloxy, cyclobutyloxy,cyclopentyloxy, cyclohexyloxy, and the like. An alkoxy group can includeabout 1 to about 12, about 1 to about 20, or about 1 to about 40 carbonatoms bonded to the oxygen atom, and can further include double ortriple bonds, and can also include heteroatoms. For example, an allyloxygroup or a methoxyethoxy group is also an alkoxy group within themeaning herein, as is a methylenedioxy group in a context where twoadjacent atoms of a structure are substituted therewith.

The term “amine” as used herein refers to primary, secondary, andtertiary amines having, e.g., the formula N(group)₃ wherein each groupcan independently be H or non-H, such as alkyl, aryl, and the like.Amines include but are not limited to R—NH₂, for example, alkylamines,arylamines, alkylarylamines; R₂NH wherein each R is independentlyselected, such as dialkylamines, diarylamines, aralkylamines,heterocyclylamines and the like; and R₃N wherein each R is independentlyselected, such as trialkylamines, dialkylarylamines, alkyldiarylamines,triarylamines, and the like. The term “amine” also includes ammoniumions as used herein.

The term “amino group” as used herein refers to a substituent of theform —NH₂, —NHR, —NR₂, —NR₃ ⁺, wherein each R is independently selected,and protonated forms of each, except for —NR₃ ⁺, which cannot beprotonated. Accordingly, any compound substituted with an amino groupcan be viewed as an amine. An “amino group” within the meaning hereincan be a primary, secondary, tertiary, or quaternary amino group. An“alkylamino” group includes a monoalkylamino, dialkylamino, andtrialkylamino group.

The terms “halo,” “halogen,” or “halide” group, as used herein, bythemselves or as part of another substituent, mean, unless otherwisestated, a fluorine, chlorine, bromine, or iodine atom.

The term “haloalkyl” group, as used herein, includes mono-halo alkylgroups, poly-halo alkyl groups wherein all halo atoms can be the same ordifferent, and per-halo alkyl groups, wherein all hydrogen atoms arereplaced by halogen atoms, such as fluoro. Examples of haloalkyl includetrifluoromethyl, 1,1-dichloroethyl, 1,2-dichloroethyl,1,3-dibromo-3,3-difluoropropyl, perfluorobutyl, and the like.

The term “monovalent” as used herein refers to a substituent connectingvia a single bond to a substituted molecule. When a substituent ismonovalent, such as, for example, F or Cl, it is bonded to the atom itis substituting by a single bond.

The term “hydrocarbon” or “hydrocarbyl” as used herein refers to amolecule or functional group that includes carbon and hydrogen atoms.The term can also refer to a molecule or functional group that normallyincludes both carbon and hydrogen atoms but wherein all the hydrogenatoms are substituted with other functional groups.

As used herein, the term “hydrocarbyl” refers to a functional groupderived from a straight chain, branched, or cyclic hydrocarbon, and canbe alkyl, alkenyl, alkynyl, aryl, cycloalkyl, acyl, or any combinationthereof. Hydrocarbyl groups can be shown as (C_(a)-C_(b))hydrocarbyl,wherein a and b are integers and mean having any of a to b number ofcarbon atoms. For example, (C₁-C₄)hydrocarbyl means the hydrocarbylgroup can be methyl (C₁), ethyl (C₂), propyl (C₃), or butyl (C₄), and(C₀-C_(b))hydrocarbyl means in certain embodiments there is nohydrocarbyl group.

The term “solvent” as used herein refers to a liquid that can dissolve asolid, liquid, or gas. Non-limiting examples of solvents are silicones,organic compounds, water, alcohols, ionic liquids, and supercriticalfluids.

The term “green solvent” as used herein refers to environmentallyfriendly solvents or biosolvents, which can be derived from processingof agricultural crops. Suitable examples of green solvents includegamma-valerolactone, ethyl lactate, C₃-C₁₀ diols, C₂-C₁₀ alcohols,propylene glycol ethers, dimethyl carbonante, acetic acid, levulinicacid, di(ethylene glycol), and 2-methyl tertahydrofuran. In someembodiments, a green solvent can be water.

The term “independently selected from” as used herein refers toreferenced groups being the same, different, or a mixture thereof,unless the context clearly indicates otherwise. Thus, under thisdefinition, the phrase “X¹, X², and X³ are independently selected fromnoble gases” would include the scenario where, for example, X¹, X², andX³ are all the same, where X¹, X², and X³ are all different, where X¹and X² are the same but X³ is different, and other analogouspermutations.

In various embodiments, salts having a positively charged counterion caninclude any suitable positively charged counterion. For example, thecounterion can be ammonium (NH₄ ⁺), or an alkali metal such as sodium(Na⁺), potassium (K⁺), or lithium (Li⁺). In some embodiments, thecounterion can have a positive charge greater than +1, which can in someembodiments complex to multiple ionized groups, such as Zn²⁺, Al³⁺ oralkaline earth metals such as Ca²⁺ or Mg²⁺.

In various embodiments, salts having a negatively charged counterion caninclude any suitable negatively charged counterion. For example, thecounterion can be a halide, such as fluoride, chloride, iodide, orbromide. In other examples, the counterion can be nitrate, hydrogensulfate, dihydrogen phosphate, bicarbonate, nitrite, perchlorate,iodate, chlorate, bromate, chlorite, hypochlorite, hypobromite, cyanide,amide, cyanate, hydroxide, permanganate. The counterion can be aconjugate base of any carboxylic acid, such as acetate or formate. Insome embodiments, a counterion can have a negative charge greater than−1, which can in some embodiments complex to multiple ionized groups,such as oxide, sulfide, nitride, arsenate, phosphate, arsenite, hydrogenphosphate, sulfate, thiosulfate, sulfite, carbonate, chromate,dichromate, peroxide, or oxalate.

The term “transition metal complex” as used herein refers to an organicor inorganic complex that includes at least one metal from Group IV, V,or VI in the periodic table.

The term “COD” as used herein refers to 1,5-cyclooctadiene. In variousembodiments, COD may additional include a pendant functional group.

The term “lignocellulosic material” or “lignocellulosic biomass” refersto a plant-based composition comprising lignin and cellulose.

In some embodiments, a catalyst comprising a metal-containing beadlinked to a transition metal complex is provided. The metal-containingbead can be made of metal, one or more metal alloys, or an inorganicsubstance that contains a metal, such as a metal oxide or metal nitride.The bead can also be a metal organic framework, such as a zeolite. Insome embodiments, the bead includes iron oxide. The iron oxide can beFe₂O₃ or Fe₃O₄. In some embodiments, the bead is magnetic. A magneticbead can be made from any suitable material that is attracted to amagnet, such as iron oxide or a neodymium-containing material such asNd₂Fe₁₄B.

The bead can have an average size of about 0.001 μm to about 100 μm. Theaverage size of the beads corresponds, in some embodiments, to the poresize of pretreated (rendered) cellulose. (Luo et al., 2011) The averagesize of a bead corresponds to the largest dimension of a bead. In someembodiments, the bead has an average size of about 0.01 μm to about 20μm, or about 1 μm to about 20 μm. The bead can have an average size ofabout 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm,17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, or 100 μm.

In various embodiments, the bead is laser etched. In various embodimentsthe bead receives a surface modification to increase reactivity, surfacearea, and/or render the surface more easily functionalized.

In various embodiments, the beads may be of the type obtained fromFerrofluids (Nashua, N.H.), such as EMG 304. EMG 304 is a water-baseddispersion of iron oxide particles with dimensions in the range of 5-15nm. Such beads can be readily functionalized using sol-gel chemistrywith a linking group and tethered to an organic compound. (Lu et al.2002)

In various embodiments, the beads may be of the type typically used inisolating biomolecules. For instance, such beads may be obtained fromBioclone, Inc. (San Diego, Calif.), including any suitable BcMag™Magnetic Beads. BcMag™ Magnetic Beads are uniform, mono-dispersed,spherical, core-shell superparamagnetic beads which consist of ananometer-scale superparamagnetic iron oxide core, completelyencapsulated by a high purity silica shell.

The beads may also be further functionalized to readily accept a linker.For example, functionalized magnetic beads having the followingfunctional groups are commercially available and may be obtained fromBioclone, Inc. (San Diego, Calif.): beads functionalized with epoxy,vinyl sulfone, thiol or iodoacetlyl (which link to a thiol functionalgroup on the catalyst); beads functionalized with hydrazide or amine(which link to a phosphate or amine functional group of the catalyst);beads functionalized with tosyl, amine, carboxy, epoxy, aldehyde (whichlink to an amine group on the catalyst). As another example,Avidin-functionalized beads can be used, which will readily accept abiotin-based linker. (Ruffert et al., Ieee Transactions On Magnetics,Vol. 50, No. 11, November 2014).

Catalyst functionalized with a linker can be obtained, e.g., via amethod adapted from Y. Lu et al. 2002, Monge-Marcet et al, Tetrahedron2013, 69, 341-348; or Monge-Marcet et al., Catal. Sci. Technol., 2011,1, 1544-1563. As an example, such procedure may comprise: mixing atrialkoxysilane having a reactive linking group, e.g., amine, with acompound, e.g., catalyst of formula I, having a suitable counterpartreactive linking group, e.g., thioisocyanate. The resultingfunctionalized, linked catalyst may be further coupled to magnetic beadsfor a sol-gel approach, also adapted from Y. Lu et al. 2002.

In some embodiments, at least a portion of the surface of the bead iscoated by a surface modifying agent. The surface modifying agent cancover 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 98%, 99%, or100% of the surface of the metal-containing bead. The surface modifyingagent can include amorphous silica. In some embodiments, themetal-containing bead is coated with amorphous silica using a sol-gelprocess. In some embodiments, the amorphous silica uniformly covers thesurface of the bead. In various embodiments, the iron oxide beads aremodified as described by Lu et al., 2002.

All publications, including non-patent literature (e.g., scientificjournal articles), patent application publications, and patentsmentioned in this specification are incorporated by reference as if eachwere specifically and individually indicated to be incorporated byreference.

Catalyst.

The present disclosure provides a nickel complex. In various embodimentsthe nickel complex can have the structure of Formula I.

wherein X is a counterion, MB is a metal-containing bead, L is a linkergroup which links MB to any portion of the rest of the nickel complexmolecule, and R1 and R2 is each independently C₁₋₁₀ alkyl, C₇₋₁₀aralkyl, C₆-C₁₂ aryl, or C₂₋₈ heterocyclyl, each of which may beoptionally substituted.

In various embodiments, R¹ and R² are independently phenyl,unsubstituted or substituted by 1-5 substituents. For example, R¹ and R²are independently:

wherein R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from H, F,Cl, Br, I, OR, OC(O)N(R)₂, CN, NO, NO₂, ONO₂, azido, CF₃, OCF₃, alkyl,aryl, cycloalkyl, aralkyl, N(R)₂, SR, SOR, SO₂R, NHSO₂R, NRSO₂R,SO₂N(R)₂, SO₃R, C(O)R, C(O)C(O)R, C(O)CH₂C(O)R, C(S)R, C(O)OR, OC(O)R,C(O)N(R)₂, OC(O)N(R)₂, C(S)N(R)₂, (CH₂)₀₋₂N(R)C(O)R, (CH₂)₀₋₂N(R)N(R)₂,N(R)N(R)C(O)R, N(R)N(R)C(O)OR, N(R)N(R)CON(R)₂, N(R)SO₂R, N(R)SO₂N(R)₂,N(R)C(O)OR, N(R)C(O)R, N(R)C(S)R, N(R)C(O)N(R)₂, N(R)C(S)N(R)₂,N(COR)COR, N(OR)R, C(═NH)N(R)₂, C(O)N(OR)R, and C(═NOR)R, heterocyclylor heteroaryl, wherein each instance of R can be independently hydrogenor alkyl, cycloalkyl, aryl, or aralkyl. In various embodiments, R³, R⁴,R⁵, R⁶ and R⁷ are each independently selected from CF₃, alkyl, aryl,cycloalkyl or aralkyl. In various embodiments, R³ and R⁷ are the same.In various embodiments R³ and R⁷ are other than H.

In various embodiments, R¹ and R² are independently 2,4,6-(Me)₃C₆H₂,2,6-(iPr)₂C₆H₃, cyclohexyl, tert-butyl or 1-adamantyl, each of which maybe unsubstituted or substituted.

In some embodiments, R¹ and R² are each

In some embodiments, R¹ and R² are each

The counterion X can be any suitable monovalent anion, such as halide,carboxylate, alkoxide, and cyanide. The linker L can be any suitablegroup that can covalently link the complex of Formula I to themetal-containing bead B. The linker L can include from 1 to 500 atoms ofH, C, N, O, S, P, F, Cl, or combinations thereof, and can include ether,ester, amide, carbonyl, carboxylate, carbamate, urea, thiourea,thioamide, thio, alkyl, alkenyl, alkynyl, heterocyclyl, heteroaryl andaryl moieties, or combinations of any of these moieties.

In various embodiments, the linker may have the structure:

wherein Z is a moiety capable of forming a covalent bond upon reactionwith silica, a moiety capable of forming a covalent bond upon reactionwith iron oxide, or a moiety resulting from such reaction;

Y³ is a bond, —CO—, —COO—, —OCO—, —CONH—, —NHCO—, —CH₂—, —NH—, —O— or—S—.

Y² is —CH₂—, —(CH₂)_(m)O—, —(CH₂)_(m)O—;

n is an integer between 1 and 20;

m is an integer between 1 and 6;

Y¹ is a bond, —CO—, —COO—, —OCO—, —CONH—, —NHCO—, —CSNH—, —NHCS—, —CSO—,—CH₂—, —NH—, —O— or —S—; and

Q is a moiety capable of forming a covalent bond upon reaction with apendant functional group installed on the R¹, R², cyclooctadiene orimidazolinium ring of Formula I, or a moiety resulting from suchreaction.

In various embodiments, the linker may have Z is Si(OR)₃, wherein R isH, C₁-C₃ alkyl, or a Si atom linked to a silica solid surface; Y³ is abond; Y² is —CH₂—; n is an integer between 1 and 5; Y¹ is a bond; Q isan isocyanate, a thioisocyanate, a —CSNH— group linked to pendantalcohol or amine group on the nickel-COD-N-heterocyclic carbene complex,a —CONH— group linked to a pendant alcohol or amine group on thenickel-COD-N-heterocyclic carbene complex; —NH₂, —OH, an amine linked toa pendant thioamide group on the nickel-COD-N-heterocyclic carbenecomplex or an oxygen linked to a pendant thioamide group on thenickel-COD-N-heterocyclic carbene complex.

In various embodiments, the linker may have Z is Si(OR)₃, wherein R isH, C₁-C₃ alkyl, or a Si atom linked to a silica solid surface; Y³ is abond; Y² is —CH₂—; n is an integer between 1 and 5; Y¹ is a bond; Q is acarbamate, urea, thiourea, or thiocarbamate.

In some embodiments, the nickel complex can have the structure ofFormula II or Formula III:

In various other embodiments, the nickel complex can have the structureof Formula IIa or Formula IIIa:

each of which is defined as in Formula II and III above, except that Ais CH₂ and j is 1-5; or A is acetyl, propanoyl, butanoyl or pentanoyland j is 1.

Such compounds of Formula II, IIa, III and IIIa may be obtainedselecting or modifying C-4 or C-5 of the imidazolinium to include apendant functional group capable of reacting with linker L. The C-4 orC-5 may be modified before or after formation of the imidazolinium orbefore or after complexation of the imidazolinium, nickel andcyclooctadiene. For example, the imidazolinium may be synthesizedaccording to Monge-Marcet et al, 2013 then complexed with nickel andcyclooctadiene. (Monge-Marcet et al, Tetrahedron 2013, 69, 341-348).Other approaches will also be readily understood to a person ofsufficient skill in view of the present disclosure. (March's AdvancedOrganic Chemistry: Reactions, Mechanisms and Structure, 5^(th) ed by M.B. Smith and J. March. Wiley Interscience: New York. 2001. 2112).

In some embodiments, the nickel complex can have the structure ofFormula IV or Formula V:

Such compounds of Formula IV and V may be obtained selecting ormodifying R¹ or R² to include a pendant functional group capable ofreacting with linker L. The R¹ or R² may be modified before or afterformation of the imidazolinium or before or after complexation of theimidazolinium, nickel and cyclooctadiene. For example, the R¹ or R² canbe modified as described in Monge-Marcet et al., 2011. (Monge-Marcet etal., Catal. Sci. Technol., 2011, 1, 1544-1563) Other approaches willalso be readily understood to a person of sufficient skill in view ofthe present disclosure. (March's Advanced Organic Chemistry: Reactions,Mechanisms and Structure, 5^(th) ed by M. B. Smith and J. March. WileyInterscience: New York. 2001. 2112).

In some embodiments, the nickel complex can have the structure ofFormula VI:

Such compounds of Formula VI may be obtained modifying thecyclooctadiene to include a pendant functional group capable of reactingwith linker L. The cyclooctadiene group may be modified before or afterof the imidazolinium, nickel and cyclooctadiene. A person of ordinaryskill would recognize various approaches to obtaining a cyclooctadienegroup having a pendant functional group. (Revell et al., “Synthesis ofFunctionalized 1,5-Cyclooctadienes by LICKOR Metalation” J. Org. Chem.,2002, 67 (17), pp 6250-6252) Other approaches will also be readilyunderstood to a person of sufficient skill in view of the presentdisclosure. (March's Advanced Organic Chemistry: Reactions, Mechanismsand Structure, 5th ed by M. B. Smith and J. March. Wiley Interscience:New York. 2001. 2112).

In various embodiments the nickel complex can have the structure ofFormula VII:

wherein R¹ and R² is each independently phenyl, unsubstituted orsubstituted by 1-5 substituents. For example, R¹ and R² can beindependently:

wherein R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from H, F,Cl, Br, I, OR, OC(O)N(R)₂, CN, NO, NO₂, ONO₂, azido, CF₃, OCF₃, alkyl,aryl, cycloalkyl, aralkyl, N(R)₂, SR, SOR, SO₂R, NHSO₂R, NRSO₂R,SO₂N(R)₂, SO₃R, C(O)R, C(O)C(O)R, C(O)CH₂C(O)R, C(S)R, C(O)OR, OC(O)R,C(O)N(R)₂, OC(O)N(R)₂, C(S)N(R)₂, (CH₂)₀₋₂N(R)C(O)R, (CH₂)₀₋₂N(R)N(R)₂,N(R)N(R)C(O)R, N(R)N(R)C(O)OR, N(R)N(R)CON(R)₂, N(R)SO₂R, N(R)SO₂N(R)₂,N(R)C(O)OR, N(R)C(O)R, N(R)C(S)R, N(R)C(O)N(R)₂, N(R)C(S)N(R)₂,N(COR)COR, N(OR)R, C(═NH)N(R)₂, C(O)N(OR)R, and C(═NOR)R, heterocyclylor heteroaryl, wherein each instance of R can be independently hydrogenor alkyl, cycloalkyl, aryl, or aralkyl. In various embodiments, R³, R⁴,R⁵, R⁶ and R⁷ are each independently selected from CF₃, alkyl, aryl,cycloalkyl or aralkyl. In various embodiments, R³ and R⁷ are the same.In various embodiments R³ and R⁷ are other than H.

In various embodiments, R¹ and R² is each independently 2,4,6-(Me)₃C₆H₂,2,6-(iPr)₂C₆H₃, cyclohexyl, tert-butyl or 1-adamantyl, each of which maybe unsubstituted or substituted.

The compound of Formula VI may be modified by any methods known in theart so as to be linked, trapped, or otherwise bound to a magnetic solidsubstrate or magnetic beads.

In various additional embodiments, the catalysts may have a structureaccording to any of Formulae VII, VIII, IX, X, XI and XII:

Such compounds may be defined as described for Formula II, III, IV, Vand VI herewith. Such compounds may be prepared as discussed herewithfor Formula II, III, IV, V and VI and using techniques known in the art.(Monge-Marcet et al, Tetrahedron 2013, 69, 341-348; Monge-Marcet et al.,Catal. Sci. Technol., 2011, 1, 1544-1563; March's Advanced OrganicChemistry: Reactions, Mechanisms and Structure, 5^(th) ed by M. B. Smithand J. March. Wiley Interscience: New York. 2001. 2112; Revell et al.,J. Org. Chem., 2002, 67 (17), pp 6250-6252).

In various embodiments the catalyst includes a magnetic bead thatincludes iron oxide and linked to a transition metal complex having thestructure of any one of Formulae I-VI.

Method of Fractionation.

The present disclosure also provides a method of fractionation. Themethod includes treating a cellulose-containing composition, such aswood or another cellulose containing material, with an effective amountof the catalyst to form a fractionated composition. The fractionatedcomposition may be formed under conditions that avoid the degradation ofany sugars, such as monosaccharides. The catalyst can retain itscatalytic activity with up to a 50% cellulose load, or about a 5%, 10%,20%, 30%, 40%, or 50% cellulose load.

In various embodiments the cellulose-containing composition is a lignin-and cellulose-containing composition, i.e., a lignocellulosiccomposition.

The treating step can include chemically fractionating thecellulose-containing composition. In some embodiments, chemicalfractionation includes selective cleavage of the β-1,4 glycosidic bondsof cellulose by the transition metal complex. Without being bound bytheory, it is believed that the chemical fractionation occurs by bindingof the catalyst active site to a cellulose polymer to cleave the β-1,4glycosidic bonds.

Cellulose polymers are composed of many non-aromatic ethers linkedtogether. The catalysts described herein can depolymerize the cellulosepolymers by reacting with the β-1,4-glycosidic linkages in the cellulosepolymers, which are the oxygen to carbon bonds that hold the glucosemonometers together, resulting in the cleavage of the 1,4-glycosidiclinkages.

The treating step can include mechanically fractionating thecellulose-containing composition. The mechanical fractionation caninclude increasing the accessible surface area and pore size of thecellulose-containing composition. The surface area and pore size arebelieved to increase as a result of mechanical agitation of thecellulose-containing composition with the catalyst. (Luo et al., 2011)That is, in various embodiments, mechanical fractionation is achievedvia mechanical agitation of the composition from the beads. For example,in some embodiments, the beads may physical act upon the cellulose poresto open and expand them, increasing the available surface area of thecellulose-containing composition. Advantageously, thecellulose-containing composition can include a softwood feedstock,rather than high quality and expensive lignin feedstock. Thus, thecellulose-containing composition can include softwood chips, cornstover, or combinations thereof.

In various embodiments, the treating step can include both chemicallyand mechanically fractionating the cellulose-containing composition.

The fractionation described herein can occur in any suitable greensolvent, or mixture of green solvents. In various embodiments, thefractionation described herein can be performed in a green solvent suchas levulinic acid, gamma-valerolactone, or mixtures thereof.

In some embodiments, the reaction of any of the catalysts of the presentdisclosure may proceed according to the following Scheme 1.

In various embodiments, the fractionation method can separate thecellulosic matrix (hemicellulose and cellulose) from the lignin in thecellulose-containing composition by conducting the reaction attemperature and for a time that separates the cellulosic network fromlignin network. In some embodiments, the fractionating is performed at atemperature of about 90° C. to about 450° C.

The fractionated composition can be formed at temperatures of about 90°C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170°C., 180° C., 190° C., 200° C., 300° C., 350° C., 400° C., or 450° C., orat any range between these temperatures, in the presence of the catalystdescribed herein. For example, fractionation can be performed at from280° C. to 400° C., 300° C. to 380° C., 320° C. to 360° C. Fractionationcan be performed at a temperature greater than, less than or about equalto 300° C., 310° C., 320° C., 330° C., 340° C., 350° C., 360° C., 370°C., 380° C., 390° C. or 400° C. The fractionated composition can beformed by reacting a cellulose-containing composition in the presence ofthe catalyst for about 10 min, 20 min, 30 min, 40 min, 50 min, 60 min,70 min, 80 min, 90 min, 2 hours, 3 hours, 4 hours, 6 hours, 8 hours, 10hours, or 12 hours, or any range between these values.

In some embodiments, the method includes magnetically separating acatalyst that includes a metal-containing bead linked to a transitionmetal complex from the fractionated composition. Magnetically separatingthe catalyst can include stirring the reaction mixture with one or moremagnets in the reaction mixture. The magnetic properties of the catalystadvantageously allow for its separation from the reaction mixture by,for example, attaching to magnets placed into the reaction mixture. Themagnet or magnets to which the catalyst attaches to can subsequently beremoved from the mixture, and the catalyst physically separated from themagnets. After separation from the reaction mixture, the catalyst can bereused several times without affecting the yield or the rate ofconversion of the cellulose to monosaccharides. In some embodiments, thecatalyst can be reused 2, 3, 4, 5, or 6 times.

The catalyst can be present in an amount from about 0.0001 wt % to about2 wt % relative to the weight of cellulose-containing composition. Insome embodiments, the catalyst is an amount of about 0.005 wt %, 0.001wt %, 0.005 wt %, 0.01 wt %, 0.05 wt %, 0.1 wt %, 0.25 wt %, 0.5 wt %,0.75 wt %, 1 wt %, 1.25 wt %, 1.5 wt %, 1.75 wt %, or 2 wt % relative tothe weight of the cellulose-containing composition.

In some embodiments, the fractionating is performed at a pressure ofabout 1 bar to about 10 bar. In some embodiments, the fractionating isperformed at a pressure of about 1 bar, 2 bar, 3 bar, 4 bar, or 5 bar, 6bar, 7 bar, 8 bar, 9 bar or 10 bar or any range between these values.For example, fractionating may be performed at a pressure between about4.75 bar to 5.25 bar, 4.5 bar to 5.5 bar, or 4 bar top 6 bar, or 3 barto 7 bar.

In various embodiments, the fractionating is performed at a pressure ofabout 1 bar to about 10 bar for about 10 minutes to about 10 hours at atemperature of about 280° C. to about 400° C. In various embodiments,the fractionating is performed at a pressure of about 4 bar to about 6bar for about 15 minutes to about 7 hours at a temperature of about 300°C. to about 380° C. In various embodiments, the fractionating isperformed at a pressure of about 1 bar to about 5 bar for about 1 hourto about 5 hours at a temperature of about 320° C. to about 360° C. Insome embodiments, the fractionating is performed at a pressure of about5 bar for about 1 hour or about 5 hours, at a temperature of about 340°C.

In various embodiments, the fractionating is performed on separatedlignin, e.g., as obtained from organsolv or other process which producesquality separated lignin, at a pressure of about 1 bar to about 10 barfor about 10 minutes to about 2 hours at a temperature of about 280° C.to about 400° C. In various embodiments, the fractionating is performedon lignin at a pressure of about 4 bar to about 6 bar for about 15minutes to about 2 hours at a temperature of about 300° C. to about 380°C. In various embodiments, the fractionating is performed on separatedlignin at a pressure of about 1 bar to about 5 bar for about 30 minutesto about 2 hours at a temperature of about 320° C. to about 360° C. Insome embodiments, the fractionating is performed on separated lignin ata pressure of about 5 bar for about 1 hour, at a temperature of about340° C.

In various embodiments, the lignin separation is performed prior tofractionation. The lignin separation is performed on thelignin-containing wood structure at less than, greater than or aboutequal to 80° C., 90° C., 100° C., 110° C., 120° C., 130° C., 140° C.,150° C., 160° C., 170° C., 180° C., 190° C., 200° C. For example, ligninseparation may be performed at between 100° C. and 200° C., between 130°C. and 190° C., or between 150° C. and 170° C. The lignin separation isperformed on the lignin-containing wood structure at less than, greaterthan or about equal to 80° C., 90° C., 100° C., 110° C., 120° C., 130°C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., 200° C. Forexample, lignin separation may be performed for about 5, about 10, about15 or about 20 minutes.

In various embodiments, the lignin separation is performed in the samestep as fractionation. The lignin separation and fractionation areperformed on the wood directly at a temperature about 90° C., 100° C.,110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C.,190° C., 200° C., 300° C., 350° C., 400° C., or 450° C., or at any rangebetween these temperatures, in the presence of the catalyst describedherein. For example, fractionation can be performed at from 280° C. to400° C., 300° C. to 380° C., 320° C. to 360° C. Fractionation can beperformed at a temperature greater than, less than or about equal to300° C., 310° C., 320° C., 330° C., 340° C., 350° C., 360° C., 370° C.,380° C., 390° C. or 400° C. The lignin separation and fractionation areperformed on the wood directly at a pressure about 1 bar, 2 bar, 3 bar,4 bar, or 5 bar, 6 bar, 7 bar, 8 bar, 9 bar or 10 bar or any rangebetween these values. For example, fractionating may be performed at apressure between about 4.75 bar to 5.25 bar, 4.5 bar to 5.5 bar, or 4bar top 6 bar, or 3 bar to 7 bar. The lignin separation andfractionation are performed on the wood directly at a pressure about 1bar, 2 bar, 3 bar, 4 bar, or 5 bar, 6 bar, 7 bar, 8 bar, 9 bar or 10 baror any range between these values. For example, fractionating may beperformed at a pressure between about 4.75 bar to 5.25 bar, 4.5 bar to5.5 bar, or 4 bar top 6 bar, or 3 bar to 7 bar. The lignin separationand fractionation are performed on the wood directly for about or atleast 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160,165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230,235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295 or 300minutes and/or no more than 300 minutes.

The lignin separation and fractionation are performed at a pressure ofabout 1 bar to about 10 bar for about 10 minutes to about 5 hours at atemperature of about 280° C. to about 400° C. In various embodiments,the fractionating is performed at a pressure of about 4 bar to about 6bar for about 15 minutes to about 5 hours at a temperature of about 300°C. to about 380° C. In various embodiments, the fractionating isperformed at a pressure of about 1 bar to about 5 bar for about 30minutes to about 5 hours at a temperature of about 320° C. to about 360°C. In some embodiments, the fractionating is performed at a pressure ofabout 5 bar for at least 30 minutes about 5 hours or less, at atemperature of about 340° C.

The fractionated composition includes a liquid phase and a solid phase.The solid phase can include lignin. The liquid phase can includemonosaccharides. In some embodiments, the yield of monosaccharides basedon the weight of the cellulose-containing composition can be 5%, 10%,15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 95%, or 99%, or any range between these values.

In some embodiments, the production of monosaccharides proceedsaccording to Scheme 2.

In various embodiments, the method includes addition of hydrogen gas(H₂) to produce the fractionated composition.

In some embodiments, a method of wood fractionation includesmechanically and chemically fractionating a cellulose-containingcomposition with a catalyst to produce a fractionated composition havinga liquid phase comprising monosaccharides and a solid phase, wherein thechemical fractionation includes selective cleavage of the β-1,4glycosidic bonds of cellulose by the transition metal complex, themechanical fractionation includes increasing the accessible surface areaand pore size of the cellulose-containing composition; and magneticallyseparating the catalyst from the fractionated composition. Themechanical fractionation can include increasing the accessible surfacearea and pore size of the cellulose-containing composition, e.g., bymechanical agitation of the composition from the beads. (Luo et al.,2011) The surface area and pore size are believed to increase as aresult of mechanical agitation of the cellulose-containing compositionwith the catalyst.

In some embodiments, a method of making a transition metal complex isprovided. The method includes reacting

with a transition metal precursor in the presence a strong base andsolvent to form a N-heterocyclic carbene complex. The method can alsoinclude reacting, e.g.,

in the presence a strong base and solvent to form a N-heterocycliccarbene carbene complex.

The strong base can be an alkali metal alkoxide, such as sodiumt-butoxide. The strong base can also be an alkali metal salt of anamine, such as lithium diisopropyl amide (LDA), or an organolithiumreagent such as butyllithium.

The solvent can be any suitable non-polar aprotic solvent, such tolueneor xylene.

The transition metal precursor can be a Ni(O) (nickel in the zerooxidation state) complex, such as Ni(COD)₂.

EXAMPLES

Various embodiments of the present invention can be better understood byreference to the following Examples which are offered by way ofillustration. The present invention is not limited to the Examples givenherein.

Synthesis of Nickel Catalyst

The below synthetic steps can be used to provide a newly synthesizedsolid catalyst, according to some embodiments.

Step 1: An aromatic amine, where R=2,4,6-trimethylaniline or2,6-diisopropylaniline, can be reacted with oxalic acid in a glyoxallinking reaction in methanol solvent for 6 h at 25° C. to form adiamine.

Step 2: The diimine from Step 1 is contacted with hydrochloric acid toform a salt.

Step 3: Forming the ring structure: Stirred and refluxed at 110° C. for16 hours under an argon atmosphere.

Step 4: The product is washed once with cold diethyl ether and once withcold ethyl acetate.

Step 5: The transition metal complex is synthesized by Ni(COD)₂ with 2.5equivalents of sodium-t-butoxide in m-xylene.

Such compound is further derivatized to contain a functional group whichwill react with a linker functional group. For example, using syntheticapproaches and techniques known in the art. (Monge-Marcet et al,Tetrahedron 2013, 69, 341-348; Monge-Marcet et al., Catal. Sci.Technol., 2011, 1, 1544-1563; March's Advanced Organic Chemistry:Reactions, Mechanisms and Structure, 5^(th) ed by M. B. Smith and J.March. Wiley Interscience: New York. 2001. 2112; Revell et al., J. Org.Chem., 2002, 67 (17), pp 6250-6252).

The functionalized compound is linked to magnetic beads as described inLu et al. 2002, which is incorporated by reference herewith, and usingEMG 304 beads obtained from Ferrofluids (Nashua, N.H.).

The terms and expressions that have been employed are used as terms ofdescription and not of limitation, and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theembodiments of the present invention. Thus, it should be understood thatalthough the present invention has been specifically disclosed byspecific embodiments and optional features, modification and variationof the concepts herein disclosed may be resorted to by those of ordinaryskill in the art, and that such modifications and variations areconsidered to be within the scope of embodiments of the presentinvention.

ENUMERATED EMBODIMENTS

The following exemplary embodiments are provided, the numbering of whichis not to be construed as designating levels of importance:

Embodiment 1 provides a catalyst having the structure:

wherein

X is a counterion;

L is a linker group;

MB is a magnetic metal-containing bead; and

R¹ and R² are each independently chosen from C₁₋₁₀ alkyl, C₇₋₁₀ aralkyl,C₆-C₁₂ aryl, or C₂₋₈ heterocyclyl, each of which may be optionallysubstituted.

Embodiment 2 provides the catalyst of embodiment 1, wherein the beadcomprises iron oxide.

Embodiment 3 provides the catalyst of any one of embodiments 1-2,wherein the bead has an average size of about 0.001 μm to about 100 μm.

Embodiment 4 provides the catalyst of any one of embodiments 1-3,wherein at least a portion of the surface of the bead is coated byamorphous silica.

Embodiment 5 provides the catalyst of any one of embodiments 1-4,wherein the linker comprises a silane on one terminal end whichcovalently binds to the silica surface of the meta-containing bead.

Embodiment 6 provides the catalyst of any one of embodiments 1-5,wherein the linker comprises a functional group on one terminal endwhich covalently binds to the functional group furnished on theremainder of the molecule.

Embodiment 7 provides the catalyst of any one of embodiments 1-6,wherein the linker is attached according to the structure:

Embodiment 8 provides the catalyst of any one of embodiments 1-7,wherein the linker is attached to the surface or silica surface of themeta-containing bead by a siloxane linkage and attached to the remainingportion of the catalyst molecule via carbamate, urea, thiocarbamate,thiourea, amide or ester linkage.

Embodiment 9 provides the catalyst of any one of embodiments 1-8,wherein R¹ and R¹ are each independently

wherein R³, R⁴, R⁵, R⁶ and R⁷ are each independently H,

C₁-C₁₀ alkyl, wherein at least a portion of the surface of the bead isuniformly coated with amorphous silica.

Embodiment 10 provides the catalyst of any one of embodiments 1-9,wherein R¹ and R² are

Embodiment 11 provides the catalyst of any one of embodiments 1-9,wherein R¹ and R² are

Embodiment 12 provides a method of fractionation, comprising:

treating a lignocellulosic feedstock with an effective amount of acatalyst immobilized on a solid magnetic support, wherein the catalystcomprises a nickel coordinated to a cyclooctadiene ligand and ann-heterocyclic carbene; and

heating the treated lignocellulosic feedstock under pressure.

Embodiment 13 provides the method of embodiment 12, wherein the catalysthas the structure of any one of Embodiments 1-12 or has the structure ofFormula I:

wherein

X is a counterion;

L is a linker group;

MB is a metal-containing solid bead support; and

R¹ and R² is each independently C₁₋₁₀ alkyl, C₇₋₁₀ aralkyl, C₆-C₁₂ aryl,or C₂₋₈ heterocyclyl, each of which may be optionally substituted.

Embodiment 14 provides the method of any one of embodiments 12-13,wherein the treating comprises mechanical and chemical degradation ofthe lignocellulosic feedstock.

Embodiment 15 provides the method of embodiment 14, wherein the chemicaldegradation comprises selective cleavage of the β-1,4 glycosidic bondsof cellulose by the transition metal complex.

Embodiment 16 provides the method of any one of embodiments 14-15,wherein the mechanical degradation is due to mechanical abrasion of thelignocellulosic feedstock by the solid support.

Embodiment 17 provides the method of any one of embodiments 14-16,wherein the mechanical degradation results in increased pore size andincreased reactive surface area of the lignocellulosic feedstock.

Embodiment 18 provides the method of any one of embodiments 12-17,wherein the lignocellulosic composition comprises softwood chips, cornstover, or a combination thereof.

Embodiment 19 provides the method of any one of embodiments 12-18,further comprising magnetically separating the catalyst from thefractionated composition.

Embodiment 20 provides the method of any one of embodiments 12-19,wherein separation of lignin and fractionation is performedsimultaneously in a single heating step.

Embodiment 21 provides a method of wood fractionation, comprising:

mechanically and chemically fractionating a cellulose-containingcomposition with a catalytic amount of the catalyst of any one ofembodiment 1-11 to produce a fractionated composition having a liquidphase comprising monosaccharides and a solid phase, wherein

the chemical fractionation comprises selective cleavage of the β-1,4glycosidic bonds of cellulose by the transition metal complex,

the mechanical fractionation comprises increasing the accessible surfacearea and pore size of the cellulose-containing composition; and

magnetically separating the catalyst from the fractionated composition.

Embodiment 22 provides a method of fractionation, comprising:

treating a lignocellulosic feedstock with the catalyst of any one ofembodiments 1-11; and heating the treated lignocellulosic feedstockunder pressure.

Embodiment 23 provides the method of any one of embodiments 12-22,wherein the fractionating is performed at a temperature of about 300° C.to 400° C., at a pressure between 1 and 10 bar, for 5 hours or less.

Embodiment 24 provides the method of any one of embodiments 12-23,wherein the method is for wood fractionation.

Embodiment 25 provides the method of any one of embodiments 12-24,wherein the catalytic amount of the composition of embodiments 1 is fromabout 0.0001 wt % to about 2 wt % relative to the weight of thecellulose-containing composition.

Embodiment 26 provides the method of any one of embodiments 12-25,wherein the fractionating is performed at a temperature of about 90° C.to about 450° C.

Embodiment 27 provides the method of any one of embodiments 12-26,wherein the fractionating is performed at a pressure of about 1 bar toabout 10 bar.

Embodiment 28 provides the method of any one of embodiments 12-27,wherein the fractionated composition comprises a liquid phase and asolid phase.

Embodiment 29 provides the method of any one of embodiments 12-28,wherein the liquid phase comprises monosaccharides.

REFERENCES

Each of the following references are hereby incorporated by reference intheir entireties:

-   1. RFA, Fueling a high octane future. 2016, Renewable Fuels    Association: on the world wide web at:    ethanolrfa.org/wp-content/uploads/2016/02/RFA_2016_full_final.pdf.-   2. Li, H., et al., Efficient valorization of biomass to biofuels    with bifunctional solid catalytic materials. Progress in Energy and    Combustion Science, 2016. 55: p. 98-194.-   3. Hu, L., et al., Chemocatalytic hydrolysis of cellulose into    glucose over solid acid catalysts. Applied Catalysis B:    Environmental, 2015. 174-175: p. 225-243.-   4. Schneider, L., et al., Solid acid-catalyzed depolymerization of    barley straw driven by ball milling. Bioresource Technology, 2016.    206: p. 204-210.-   5. Rinaldi, R., et al., Which controls the depolymerization of    cellulose in ionic liquids: The solid acid catalyst or cellulose?    ChemSusChem, 2010. 3(2): p. 266-276.-   6. Onda, A., T. Ochi, and K. Yanagisawa, Selective hydrolysis of    cellulose into glucose over solid acid catalysts. Green    Chemistry, 2008. 10(10): p. 1033-1037.-   7. Zhang, C., et al., Biochar sulfonic acid immobilized    chlorozincate ionic liquid: an efficiently biomimetic and reusable    catalyst for hydrolysis of cellulose and bamboo under microwave    irradiation. Cellulose, 2014. 21(3): p. 1227-1237.-   8. Verma, D., R. Tiwari, and A. K. Sinha, Depolymerization of    cellulosic feedstocks using magnetically separable functionalized    graphene oxide. RSC Advances, 2013. 3(32): p. 13265-13272.-   9. Xiong, Y., et al., Hydrolysis of cellulose in ionic liquids    catalyzed by a magnetically-recoverable solid acid catalyst.    Chemical Engineering Journal, 2014. 235: p. 349-355.-   10. Shuai, L. and X. Pan, Hydrolysis of cellulose by    cellulase-mimetic solid catalyst. Energy & Environmental    Science, 2012. 5(5): p. 6889-6894.-   11. Alonso, D. M., S. G. Wettstein, and J. A. Dumesic,    Gamma-valerolactone, a sustainable platform molecule derived from    lignocellulosic biomass. Green Chemistry, 2013. 15(3): p. 584-595.-   12. Luo, X. et al., Effects of drying-induced fiber hornification on    enzymatic saccharification of lignocelluloses. Enzyme and microbial    technology, 2011. 48(1): p. 92-99.-   13. Lu, Y., et al., Modifying the surface properties of    superparamagnetic iron oxide nanoparticles through a sol-gel    approach. Nano letters, 2002. 2(3): p. 183-186.-   14. Ruffert, C, et al., Investigations on the Separation of Platinum    Nanoparticles With Magnetic Beads Ieee Transactions On Magnetics,    Vol. 50, No. 11, November 2014-   15. Monge-Marcet, A. et al., Imidazolium-derived organosilicas for    catalytic applications, Catal. Sci. Technol., 2011, 1, 1544-1563-   16. Revell, J. D., et al., Synthesis of Functionalized 1,    5-Cyclooctadienes by LICKOR Metalation J. Org. Chem., 2002, 67 (17),    pp 6250-6252-   17. Monge-Marcet, A., et al, Catalytic applications of recyclable    silica immobilized NHC-ruthenium complexes, Tetrahedron 2013, 69,    341-348-   18. March's Advanced Organic Chemistry: Reactions, Mechanisms and    Structure, 5^(th) ed by M. B. Smith and J. March. Wiley    Interscience: New York. 2001. 2112;

What is claimed is:
 1. A catalyst having the structure:

wherein X is a counterion; L is a linker group; MB is a magneticmetal-containing bead; and R¹ and R² is each C₁₋₁₀ alkyl, C₇₋₁₀ aralkyl,C₆-C₁₂ aryl, or C₂₋₈ heterocyclyl, each of which may be optionallysubstituted.
 2. The catalyst of claim 1, wherein the bead comprises ironoxide.
 3. The catalyst of claim 1, wherein the bead has an average sizeof about 0.001 μm to about 100 μm.
 4. The catalyst of claim 1, whereinat least a portion of the surface of the bead is coated by amorphoussilica.
 5. The catalyst of claim 4, wherein the linker comprises asilane on one terminal end which covalently binds to the silica surfaceof the metal-containing bead.
 6. The catalyst of claim 1, wherein thelinker comprises a functional group on one terminal end which covalentlybinds to the functional group furnished on the remainder of themolecule.
 7. The catalyst of claim 1, wherein the linker is attachedaccording to the structure:


8. The catalyst of claim 1, wherein the linker is attached to the silicasurface of the metal-containing bead by a siloxane linkage and attachedto the remaining portion of the catalyst molecule via carbamate, urea,thiocarbamate, thiourea, amide or ester linkage.
 9. The catalyst ofclaim 1, wherein R¹ and R² are each independently

wherein R³, R⁴, R⁵, R⁶ and R⁷ are each independently H, C₁-C₁₀ alkyl,wherein at least a portion of the surface of the bead is uniformlycoated with amorphous silica.
 10. The catalyst of claim 9, wherein R¹and R² are


11. The catalyst of claim 9, wherein R¹ and R² are


12. A method of fractionation, comprising: treating a lignocellulosicfeedstock with an effective amount of a catalyst immobilized on a solidmagnetic support, wherein the catalyst comprises a nickel coordinated toa cyclooctadiene ligand and an n-heterocyclic carbene; and heating thetreated lignocellulosic feedstock under pressure.
 13. The method ofclaim 12, wherein the catalyst has the structure of Formula I:

wherein X is a counterion; L is a linker group; MB is a metal-containingsolid bead support; and R¹ and R² is each independently C₁₋₁₀ alkyl,C₇₋₁₀ aralkyl, C₆-C₁₂ aryl, or C₂₋₈ heterocyclyl, each of which may beoptionally substituted.
 14. The method of claim 13, wherein the treatingcomprises mechanical and chemical degradation of the lignocellulosicfeedstock.
 15. The method of claim 14, wherein the chemical degradationcomprises selective cleavage of the β-1,4 glycosidic bonds of celluloseby the transition metal complex.
 16. The method of claim 14, wherein themechanical degradation is due to mechanical abrasion of thelignocellulosic feedstock by the solid support.
 17. The method of claim12, further comprising magnetically separating the catalyst from thefractionated composition.
 18. The method of claim 12, wherein separationof lignin and fractionation is performed simultaneously in a singleheating step.
 19. A method of wood fractionation, comprising:mechanically and chemically fractionating a cellulose-containingcomposition with a catalytic amount of the catalyst of claim 1 toproduce a fractionated composition having a liquid phase comprisingmonosaccharides and a solid phase, wherein the chemical fractionationcomprises selective cleavage of the β-1,4 glycosidic bonds of celluloseby the transition metal complex, the mechanical fractionation comprisesincreasing the accessible surface area and pore size of thecellulose-containing composition; and magnetically separating thecatalyst from the fractionated composition.
 20. The method of claim 18,wherein the fractionating is performed at a temperature of about 300° C.to 400° C., at a pressure between 1 and 10 bar, for 5 hours or less.